diff --git a/src/devices/devices_toc.cs b/src/devices/devices_toc.cs
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--- a/src/devices/devices_toc.cs
+++ b/src/devices/devices_toc.cs
@@ -37,6 +37,7 @@
           <li><a href="<?cs var:toroot ?>devices/audio_avoiding_pi.html">Avoiding Priority Inversion</a></li>
           <li><a href="<?cs var:toroot ?>devices/latency_design.html">Design For Reduced Latency</a></li>
           <li><a href="<?cs var:toroot ?>devices/audio_terminology.html">Terminology</a></li>
+          <li><a href="<?cs var:toroot ?>devices/testing_circuit.html">Testing Circuit</a></li>
         </ul>
       </li>
       <li><a href="<?cs var:toroot ?>devices/camera.html">Camera v1</a></li>
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diff --git a/src/devices/testing_circuit.jd b/src/devices/testing_circuit.jd
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@@ -0,0 +1,74 @@
+page.title=Testing Circuit
+@jd:body
+
+<div id="qv-wrapper">
+  <div id="qv">
+    <h2>In this document</h2>
+    <ol id="auto-toc">
+    </ol>
+  </div>
+</div>
+
+<p>
+The file <a href="http://developer.android.com/downloads/partner/audio/av_sync_board.zip">av_sync_board.zip</a>
+contains CAD files for an A/V sync and latency testing
+printed circuit board (PCB).
+The files include a fabrication drawing, EAGLE CAD, schematic, and BOM.
+</p>
+
+<p>
+This PCB
+can be used to help measure the time between flashing the device's
+notification LED or screen backlight, vs. detecting an audio signal.
+When combined with a dual-channel oscilloscope and suitable test app,
+it can show the difference in time between detecting the light and audio.
+That assumes the LED or backlight response time and light detector's response time
+are negligible relative to the audio.
+</p>
+
+<p>
+This design is supplied "as is", and we aren't be responsible for any errors in the design.
+But if you have any suggestions for improvement, please post to android-porting group.
+</p>
+
+<p>
+Of course, this is not the only (or necessarily best) way to measure A/V sync and latency,
+and we would like to hear about your alternative methods, also at android-porting group.
+</p>
+
+<p>
+There are currently no compatibility requirements to use this particular PCB.
+We supply it to encourage your continued attention to audio performance.
+</p>
+
+<h2 id="images">Images</h2>
+
+<p>
+These photos show the circuit in action.
+</p>
+
+<img style="margin:1.5em auto" src="image1.jpg" alt="breadboard prototype" />
+<br />
+<center>Breadboard prototype</center>
+
+<img style="margin:1.5em auto" src="image2.jpg" alt="an early run of the PCB" />
+<br />
+<center>An early run of the PCB</center>
+
+<img style="margin:1.5em auto" src="image3.jpg" alt="example display">
+<br />
+<center>Example display</center>
+<p>
+This image
+shows the scope display for an unspecified device, software release, and test conditions;
+the results are not typical and cannot be used to extrapolate to other situations.
+</p>
+
+<h2 id="video">Video</h2>
+
+<p>
+This <a href="http://www.youtube.com/watch?v=f95S2IILBJY">Youtube video</a>
+shows the the breadboard version testing circuit in operation.
+Skip ahead to 1:00 to see the circuit.
+</p>
+